The answer to this question is something I've been scared to know but I think I finally have the courage to ask.
I bought a 70+ year old Chicago brick bungalow and have been restoring the wood, trim and floors, with help from this site, using citristrip and the procedure outlined by Henry in MI.
I noticed as I was sanding the floors in the last room I redid that there was noticeable slope; one end is lower than the other. This slope is roughly over a crack in the basement wall trough which water flows during very bad spring rain. I should point out at this point that the inspector told me this crack was nothing to worry about during the final walk-through.
Also there is a chimney roughly above all this that seems to lean to one side maybe by 10-15 degrees or so.
I think my question comes down to the difference between 'my house has settled' which doesn't sound so bad and 'my house needs $50k of repairs' which is what I'm frightene of.
I can say that there has been no movement of any walls, floors etc. since we moved in 18 months ago.